1. Field of the Invention
The present invention relates to sugar syrup-based ant baits, to a process for the production of these ant baits and to their use.
2. Description of Related Art
It is known that insecticides can be employed in a wide variety of preparation forms in the control of ants. For example, mention may be made of spray compositions, dusts, spray cans and baits. Since ants are often found within fairly close living range of humans and of domestic animals and must be controlled there, bait preparations are increasingly gaining in importance because of their comparatively low endangerment of humans and domestic animals and because of their very generally high environmental friendliness. Furthermore, baits containing a slow-acting insecticide make possible introduction into the nest by the ants. Feeding to further harvesting ants, queen(s) and larvae (trophallaxis) leads to complete eradication of the colony, which can scarcely be achieved using other processes.
The number of insecticidal active substances which are suitable for use in an ant bait, however, is very low, since the ants, which react very sensitively, usually refuse their acceptance. This applies particularly if the baits have to contain active substances in high concentrations in order to achieve a satisfactory high activity.
As insecticidally and acaricidally active substances which can be employed for the control of ants, for example, O,O-diethylthionophosphoryl-α-oximinophenylacetonitrile (phoxim) and O,O-diethylthionophosphoryl-α-oximino-(2-chlorophenyl)acetonitrile (chlorophoxim) have already been known for many years (cf. German Patent Specification 1 238 902). These substances can be applied in the form of spray and dust compositions.
It has furthermore been attempted to employ phoxim for the control of ants in the form of a bait formulation (cf. “Toxicological and Biological Studies of Odorous House Ant, Tapinoma sessile” in Joum, of econ. Ent. Vol. 63, 1971-1973 (1970)). It resulted here that complete control of the ants can be achieved by means of baits which contain 0.05% by weight of phoxim as a mixture with blackberry syrup or blackberry jam. It is disadvantageous, however, that baits having such a low content of phoxim do not have sufficiently long storage stability for practical purposes. Analogous baits, in which the phoxim is present in a concentration of 0.5% by weight to 1% by weight, indeed have a stability and a duration of action sufficient for practical purposes, but exhibit a repellent action, so that the ants do not feed on these baits. The use of baits which contain phoxim has thus not yielded the desired success in ant control up to now. Finally, phoxim acts relatively rapidly, so that the trophallaxis described above does not occur or occurs only to a small extent.
Ant baits which also contain glycerol and/or honey in addition to phoxim and/or chlorphoxim, which however, also do not satisfactorily solve the disadvantages described above, are furthermore known from EP-A1-0 084 310.
An additional difficulty in the production of phoxim- and/or chlorphoxim-based baits lies in the fact that the active substances are relatively temperature-sensitive. Therefore the implementation of the customary production method, which consists in blending and warming the components in order to reduce the viscosity of the corresponding mixture and to make it more easily stirrable, has to be ruled out.
It has moreover emerged that ants particularly prefer liquid baits. The intake of liquid baits is simplest, and thus preferred, for the harvesting ants, which are specialized in the search for and assimilation of food. A disadvantage of liquid baits, however, is that the water content after application can fall to zero due to evaporation (drying out). This phenomenon has a disadvantageous effect on the consumption of the bait by the ant, due to the solidification of the bait and also due to concentration of the active substance contained (repellent effect). For the reasons mentioned, liquid baits are indeed very attractive initially (for 24 h), but they then lose their action rapidly.